Конструкциялық материалдар және термоөңдеу Конструкционные материалы и термообработка Constructional materials and heat treatment Учебное пособие для специальности: 5В071200– «Машиностроение»

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4. Machine-building cemented alloyed steel. Machine-building improved steel.
Maraging high-resistance steel. Spring steel. 
5. Wear-resistance constructional steel . Corrosion-resistant steel. Heat-resistant 
steel. 
General information about alloyed steel. 
The elements which are specially entered into steel for the purpose of giving 
by her demanded properties, call alloying, and the steel containing such 
elements, call alloyed. 
To destination alloyed steel can be divided into three groups: 
- the alloyed constructional. 
- the alloyed tool. 
- there were also alloys with special physical and chemical characteristics. 
Alloying of constructional steel is made for the purpose of increase of its 
strength properties. As the greatest increase of durability of the alloyed steel can 
be reached only owing to heat treatment, the second problem of an alloying of 
steel is ensuring of heat treatment in big sections, i.e. increase of hardness 
penetration of steel. 
Alloyed tool steel, except the best thermal treatment, differ the increased wear 
resistance and heat resistance. 
At introduction of a significant amount of alloying elements of steel gains new 
properties: big corrosion resistance, thermal stability, not magnetization or, on 
the contrary, gets very big coercive force, etc. 
Influence of alloying elements. 
High constructional durability of steel is provided with the rational contents in 
it alloying elements. The excess alloying (except for nickel) after achievement 
of a necessary hardness penetration leads to decrease in viscosity and promotes 
fragile destruction of steel. 
Chrome in quantity to 2% has beneficial impact on mechanical properties of 
constructional steel. 
Nickel - the most valuable alloying element. It put into quantity from 1 to 5%. 
Manganese put into steel to 1,5%. It considerably raises a limit of fluidity of 
steel, but does steel sensitive to an over heat. 
Silicon considerably raises a limit of fluidity of steel and at the contents more 
than 1% reduces viscosity and raises a cold brittleness threshold. 
Molybdenum and tungsten in number of 0,2-0,4% and 0,8-1,2% respectively, 
in complex alloyed steel promote grain crushing, increase a hardness penetration 
and worsen some other properties. 
Vanadium and the titan put into a small amount (to 0,3% of tungsten and 0,1% 
of the titan) in the steel, containing chrome, manganese, nickel, for grain 
crushing. 
The raised content of vanadium, molybdenum and tungsten in constructional 
steel isn't admissible because of formation of almost insoluble carbides when 

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heating these elements. Excess carbides, settling down on borders of grains, 
promote fragile destruction and reduce a steel hardness penetration. 
Pine forest enter for increase in a hardness penetration and in very small 
amounts (0,002-0,005%). 

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